i am using lily de silva's pali primer, im finding some things here confusing. I read elsewhere, regarding the importance of proper pronunciation of long vowels as the meaning is drastically changed, the example they used was the prefix ā, versus a. It stated the prefix 'ā' enhances the word, while 'a' negates the word. Then in lily de silva's book, gacchati for example is goes, and āgacchati is comes. So this directly contradicts what i had read elsewhere. just wondering which is correct, there are many other examples in the pali primer in which an 'ā' is used as a prefix to mean the opposite. thank you in advance, also, im sorry if this is posted elsewhere

The prefix ā- exhibits quite a range of semantic functions, both basic and idiomatic. However, since de Silva’s book is a primer, not a comprehensive reference grammar, it’s no surprise that she doesn’t wish to overburden new students by describing all of them.

In the Section on Prefixative Words (Opasaggikapada) in the Padarūpasiddhi, the grammarian Buddhapiya summarised the uses of the prefix -ā as follows:

4. Abhividhimhi: ākumāraṃ yaso kaccāyanassa.For the sake of complimenting by highlighting something surprising or unexpected, as in, ‘Kaccāyana’s fame, even though he was yet a child’.

5. Pattiyaṃ: āpattimāpannoIn the sense of ‘reaching or arriving at’, as in ‘arriving at [= falling into] a Vinaya offence’.

6. Icchāyaṃ: ākaṅkhā,In the sense of ‘wishing’, as in ‘desire’.

7. Parissajane: āliṅganaṃIn the sense of ‘[literally or figuratively] embracing’, as in ‘enclasping’.

8. Ādikamme ārambho.In the sense of ‘commencing action’, as in ‘initiating’.

9. Gahaṇe: ādīyati ālambati.In the sense of ‘taking’, as in the verbs ‘to take’ and ‘to hold’.

10. Nivāse: āvasatho.In the sense of ‘residence’, as in ‘refuge place’.

11. Samīpe: āsannaṃ.In the sense of ‘propinquity’, as in ‘near’.

12. Avhāne: āmantesi.In the sense of ‘addressing’, as in ‘he addressed’.

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As for a-, Pali grammarians don’t regard this as a prefix in the strict sense (i.e. as an upasagga). Rather, it is simply one of the forms that the indeclinable particle ‘na’ can take when it occurs as the first item in a compound. Its semantic range is rather broad, coinciding fully with those of the prefixes ‘ni’ and ‘paṭi’ and partially with that of ‘vi-’.